Re: [fluka-discuss]: less than 20 MeV neutrons

From: Francesco Cerutti <Francesco.Cerutti_at_cern.ch>
Date: Wed, 30 Jul 2014 11:54:21 +0200

Dear Takashi,

no surprise. 20 MeV is exactly the threshold below which neutrons are
treated through multigroup approach, which does not envisage the explicit
production of charged secondaries but of photons and neutrons only (apart
from specific exceptions), that's why you cease to see them (and cannot
see them), according to what is explicitly said in the manual (10.3.3). At
the same time, their contribution to energy deposition is taken into
account (in the kerma approximation).

Best wishes

Francesco

**************************************************
Francesco Cerutti
CERN-EN/STI
CH-1211 Geneva 23
Switzerland
tel. ++41 22 7678962
fax ++41 22 7668854

On Tue, 29 Jul 2014, Maruyama, Takashi wrote:

> I am trying to find energy deposition in a 320 micron-thick Silicon layer from incident neutrons. The neutron energy is monochromatic and set by the BEAM card. When I use the energy density per region in .out file, everything looks good; the energy deposition varies smoothly at 20 MeV. I wanted to find what particles are contributing to the energy depositions. So I use mgdraw to dump these particles. Above 20 MeV neutron incident, I see many recoil protons, 4He and some e-'s contributing to the energy deposition. However, as soon as I cross 20 MeV neutron energy, these recoil protons and 4He disappear, and only e-'s are present. There must be a switch or threshold for recoil particle tracking, but I cannot figure out what. Please help.
>
> Takashi Maruyama
> SLAC
>
>
Received on Wed Jul 30 2014 - 13:32:57 CEST